Chemical sensors are widely used in industrial environments for process control, environmental control, and other applications. A chemical sensor is a device that monitors the concentration of a given chemical species in a liquid or a gas. Chemical sensors are often required to be highly sensitive in order to detect small concentrations of particular chemical species. They are also often required to withstand harsh chemical environments or high temperatures that may be present in process control, environmental control, or other applications. Various oxygen sensors have been used in ambient or in harsh environmental conditions, such as high radiation levels, high corrosion rates, high humidity levels, or in high temperatures.
There is an increased need for oxygen (O2) sensors operating at high temperature and in adverse environments, such as highly corrosive environments or environments with high level of vibration. Increasingly, oxygen detectors are required in cars, aircrafts, and industrial applications to reduce emission and to monitor and optimize combustion. As oxygen sensors are often located adjacent to or within combustion engines, these oxygen sensors need to withstand ambient temperatures of at least 450° C. When mounted in furnaces, incinerators, or industrial boilers, in-situ oxygen detectors are required to cope with maximum operating temperatures ranging from 500° C. to 1600° C. Previous approaches for oxygen sensors included, amongst others, the use of semiconductors such as silicon or silicon carbide. However, the previous oxygen sensors require significant power consumption, and do not match the sensitivity level, response time, dimensions, and lifetime required for operation in harsh conditions.